A microprocessor may include the ability to run in various modes. For example, some processor cores licensable from ARM Holdings plc, Cambridge, UK, can run in a user mode as well as a privileged mode. Privileged mode is typically used by operating system (OS) processes, and user mode is typically used by application processes.
Processors may also include the ability to run processes in a secure mode or non-secure mode, and may be able to access secure resources and non-secure resources. For example, secure processes may be able to access secure resources, and non-secure processes may be able to access non-secure resources.